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Do anticoagulants improve migraine?

A frequently asked question

The Migraine Trust is often asked about the affect of anticoagulants from people who are taking the medication for another health condition and notice a change in their migraine attacks. The below is an example of such an enquiry, with an answer kindly provided by Dr Brendan Davies who is the Clinical and Research Lead at the Midlands Regional Headache Clinic, Royal Stoke University Hospital and a Trustee of The Migraine Trust.

I’ve had frequent migraine attacks since I was 13 and am now 62. I had a pulmonary embolism a year ago and have taken warfarin ever since, and I have not had a migraine attack during this period. I’ve been looking at internet forums and it seems to be a widespread experience, i.e. no migraine attacks whilst taking anticoagulants. Is there any research that could help explain this?

The simple answer to this question is that there is insufficient research in this area and so far the only studies that have been done are small and methodologically flawed.

There are several reports of patients with migraine entering remission after receiving treatment with anticoagulants such as heparin or warfarin. The earliest report I am aware of is from 1973. It is, however, strongly debated whether these are simply anecdotal coincidences or an effect of warfarin on a particular mechanism involved in migraine attack generation. It is thus unclear whether any, or only a select group of migraine sufferers who also have a tendency to clot more easily, benefit. The published data in this area is lacking in scientific rigour, but I have summarised some of the literature below.

A questionnaire survey of 400 patients in Spain on anticoagulation treatment (i.e. warfarin or a similar agent) identified 66 migraine sufferers, and two thirds of this group reported a subjective improvement in the severity and frequency of their migraine after starting anticoagulants (Morales-Asín F et al. (2000) Headache).

A further retrospective study of a small number of individuals from Holland (N= 92, Rahimtoola et al. (2001) Headache) looked at the use of acute abortive medications for migraine in patients who had been prescribed either aspirin or warfarin for a variety of reasons. This small study reported an approximate 50 percent reduction in the need for acute migraine abortive medication in the warfarin treatment group in contrast to an approximate 20 percent reduction in an aspirin treated group. Sensibly the authors suggested the need for a more robust blinded randomised clinical trial to identify if this was a true effect.

Regrettably there are still no methodologically robust doubleblind placebo controlled trials that test the hypothesis that warfarin treatment is reliably beneficial in migraine prevention. There is one randomised, unblinded, crossover study of 19 migraine patients where a warfarin like anticoagulant (acenocoumarol) was compared to propranolol treatment over two 12 week periods (Wammes-van der Heijden EA et al.,(2005) Headache). The study found no beneficial effects of the anticoagulant on migraine frequency.

Thus at present we have no good evidence apart from anecdote to suggest that warfarin is a useful agent to try in migraine prophylaxis. It is equally worth noting that warfarin also comes with a bleeding risk.

The more difficult question to answer, however, is what mechanism would be implicated were warfarin to be beneficial for migraine? There remains debate around this topic.

There is also a condition called Antiphospholipid Syndrome known to be associated with hypercoagulability (i.e. increased stickiness of the blood) which presents with an increased
tendency to thrombosis. Such individuals with this disorder are thought to have a higher incidence of migraine. There are however no good placebo-controlled trials in this condition
that suggests warfarin anticoagulation is a reliably effective treatment to reduce the frequency of migraine.

"At present we have no good evidence apart from anecdote to suggest that warfarin is a useful agent to try in migraine prophylaxis."
Dr Brendan Davies